The subject of this invention is a system design to overcome the aerodynamic forces which are exerted on a non-symmetrical object rotating around a fixed axis, with the principal application of dynamic balancing of man-made satellites.
The dynamic balancing of an object in rotation around an axis consists of modifying the distribution of the masses within this object in order to either cancel out the alterating forces on the spokes of the shaft if it is in a fixed installation (electric motor, gyroscope, or turbine), or to make its rotation around the shaft free and stable (shaping machine satellite).
This modification in the distribution of masses is accomplished by reducing the amount of matter (electric motor, gyroscope) or adjustment of the balancing of masses (satellite).
An object is simple in its rotation around its axes of inertia. The purpose of dynamic balancing is to bring into synchronization a given axis of the object and one of the principal axes of inertia. Dynamic balancing has as a necessary corollary static balancing.
The definition of the characteristics of an object rotating around an axis is accomplished by means of a balancing machine consisting of a rotating shaft connected first, rigidly to an object where characteristics are to be defined, and secondly, through a force meter to an infinitely rigid and stable structure. The data generated by these meters make it possible to measure the forces generated by the object in rotation around an axis. These force readings, in association with the parameters for the angular and geometric speed of the object, make it possible to locate and to quantify the masses to be removed or to be adjusted on the object in order to balance it, that is, to overcome the forces measured by the balancing machine.
Since the forces generated by the rotating object are proportional to the square of the speed of rotation, the measure must be made at the maximum speed compatible with rigidity and the mechanical strength of the rotating object.
The dynamic balancing of satellites is a specific activity characterized by the use of a balancing machine with a vertical shaft, a low speed of rotation (30 to 60 revolutions/min) and considerable precision in measurement.
Current satellites are characterized by an exterior which carries numerous protruding objects (antennas, reflectors, power supplies) which create during rotation considerable aerodynamics forces which are taken into account by the balancing machine, but which are fictitious masses which falsify the measurements and therefore make correct balancing of these satellite extremely difficult.
The customary method for resolving this problem consists of performing the measurements in a vacuum, which requires a sealed chamber surrounding the balancing machine system and the satellite, and the installation of the necessary pumps.